Knowledge of time expressions is crucial to speaking Spanish! When you know these expressions, you will understand whether the speaker is referring to the present, past or future.

hoy - today
ayer - yesterday
anteayer - the day before yesterday
ayer tarde - yesterday afternoon
ayer por la tarde - yesterday afternoon

el lunes que viene - next Monday
el año que viene - next year

cada mes - each month
cada año - each year

Hace una hora. - An hour ago.
hace horas - hours ago
hace un mes - a month ago

Es tarde. - It's late.
Es temprano. - It's early.

There are expressions for “In the morning/afternoon/evening” when they refer to a specific time or specific period of time.

de la mañana
in the morning (specific time)

Ya son las once de la mañana.
Already it is eleven in the morning.

de la tarde
in the afternoon (specific time)

Entre dos y cuatro de la tarde.
Between two and four in the afternoon.

de la noche
in the evening or night (specific time)

Hasta las ocho de la noche.
Until eight (8:00) in the evening.

Note: One uses en la manãna/tarde/noche or por la manãna/tarde/noche to express “during the morning” or “at night”.

Ella baña al bebé por la mañana.
She bathes the baby in the morning.

Lo puede recoger mañana en la mañana.
You can pick it up tomorrow morning.

ayer por la tarde
yesterday afternoon

Vuelve a casa por la tarde.
She returns home in the afternoon.

“Time”: vez vs. tiempo vs. hora

Tiempo (in addition to meaning “weather”) refers to time in the general or abstract sense, similar to “era” or “epoch” or as time as something which passes:

• Estos tiempos son difíciles.
  These times are hard.
• No tengo tiempo para leer nada.
  I don't have time to read anything.

Vez means time in the sense of “occurrence”; it is also used in such expressions as "muchas veces" (“often”, “many times”), "una vez" (“once”) , and "a veces" or "algunas veces" (“sometimes” or “at times”).

• Esta vez voy a ganar.
  This time I'm going to win.
• Muchas veces voy al cine a solas.
  I often go to the movies by myself.
• A veces [o: Algunas veces] es mejor esperar un poco.
  Sometimes it's better to wait a while.

Hora refers to a specific time of the day:

• Es (la) hora de comer.
  It's time to eat.
• ¿Sabes la hora? ¿Qué hora es?
  Do you know the time? What time is it?